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/* dgamlm.f -- translated by f2c (version 20041007).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#define V3P_NETLIB_SRC
#include "v3p_netlib.h"
/* Table of constant values */
static integer c__1 = 1;
static integer c__2 = 2;
/* DECK DGAMLM */
/* Subroutine */ int dgamlm_(doublereal *xmin, doublereal *xmax)
{
/* System generated locals */
doublereal d__1, d__2;
/* Builtin functions */
double log(doublereal);
/* Local variables */
integer i__;
doublereal xln, xold;
extern doublereal d1mach_(integer *);
doublereal alnbig, alnsml;
extern /* Subroutine */ int xermsg_(char *, char *, char *, integer *,
integer *, ftnlen, ftnlen, ftnlen);
/* ***BEGIN PROLOGUE DGAMLM */
/* ***PURPOSE Compute the minimum and maximum bounds for the argument in */
/* the Gamma function. */
/* ***LIBRARY SLATEC (FNLIB) */
/* ***CATEGORY C7A, R2 */
/* ***TYPE DOUBLE PRECISION (GAMLIM-S, DGAMLM-D) */
/* ***KEYWORDS COMPLETE GAMMA FUNCTION, FNLIB, LIMITS, SPECIAL FUNCTIONS */
/* ***AUTHOR Fullerton, W., (LANL) */
/* ***DESCRIPTION */
/* Calculate the minimum and maximum legal bounds for X in gamma(X). */
/* XMIN and XMAX are not the only bounds, but they are the only non- */
/* trivial ones to calculate. */
/* Output Arguments -- */
/* XMIN double precision minimum legal value of X in gamma(X). Any */
/* smaller value of X might result in underflow. */
/* XMAX double precision maximum legal value of X in gamma(X). Any */
/* larger value of X might cause overflow. */
/* ***REFERENCES (NONE) */
/* ***ROUTINES CALLED D1MACH, XERMSG */
/* ***REVISION HISTORY (YYMMDD) */
/* 770601 DATE WRITTEN */
/* 890531 Changed all specific intrinsics to generic. (WRB) */
/* 890531 REVISION DATE from Version 3.2 */
/* 891214 Prologue converted to Version 4.0 format. (BAB) */
/* 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ) */
/* ***END PROLOGUE DGAMLM */
/* ***FIRST EXECUTABLE STATEMENT DGAMLM */
alnsml = log(d1mach_(&c__1));
*xmin = -alnsml;
for (i__ = 1; i__ <= 10; ++i__) {
xold = *xmin;
xln = log(*xmin);
*xmin -= *xmin * ((*xmin + .5) * xln - *xmin - .2258 + alnsml) / (*
xmin * xln + .5);
if ((d__1 = *xmin - xold, abs(d__1)) < .005) {
goto L20;
}
/* L10: */
}
xermsg_("SLATEC", "DGAMLM", "UNABLE TO FIND XMIN", &c__1, &c__2, (ftnlen)
6, (ftnlen)6, (ftnlen)19);
L20:
*xmin = -(*xmin) + .01;
alnbig = log(d1mach_(&c__2));
*xmax = alnbig;
for (i__ = 1; i__ <= 10; ++i__) {
xold = *xmax;
xln = log(*xmax);
*xmax -= *xmax * ((*xmax - .5) * xln - *xmax + .9189 - alnbig) / (*
xmax * xln - .5);
if ((d__1 = *xmax - xold, abs(d__1)) < .005) {
goto L40;
}
/* L30: */
}
xermsg_("SLATEC", "DGAMLM", "UNABLE TO FIND XMAX", &c__2, &c__2, (ftnlen)
6, (ftnlen)6, (ftnlen)19);
L40:
*xmax += -.01;
/* Computing MAX */
d__1 = *xmin, d__2 = -(*xmax) + 1.;
*xmin = max(d__1,d__2);
return 0;
} /* dgamlm_ */
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